Machine for forming webs from fibers



Sept. 4, 1962 E. c. RUST, JR., ETAL 3,051,998

MACHINE FOR FORMING WEBS FROM FIBERS Filed June 27, 1960 corporation ofMassachusetts Filed June 27, 1960, Ser. No. 39,136 9 Claims. (CL 19-156)This invention relates to machines for forming fibers into webs ornon-woven fabrics. More particularly, the invention relates to animproved web-forming machine which is operable continuously at highspeeds to produce continuously a web of randomly disposed fibers, whichis of uniform thickness and consistency.

In prior web-forming machines, the fibers are delivered to a rotatingtoothed cylinder, as from a lap roll from which the fibers pass betweena pair of feed rolls located adjacent the peripheral portion of thetoothed cylinder. The teeth on the rotating cylinder pick up the fibersand carry them partly around the cylinder axis to a duct into which thefibers are discharged from the teeth. This duct leads to the perforatedcylindrical surface of a rotating drum in which a partial vacuum ismaintained, so that the fibers entering the duct from the cylinder teethare drawn along the duct and deposited in the form of a Web on theperforated surface of the drum. As the drum rotates, the web is removedfrom the perforated surface at a region where the suction created by thepartial vacuum in the drum is ineffective to prevent such removal.

To obtain a high rate of production, it is desirable to drive thetoothed cylinder at high speed and to arrange the duct so that itextends generally tangentially from the peripheral portion of thecylinder in the direction of its rotation. This means that the ductshould form an edge disposed in closely spaced relation to theperipheral portion of the cylinder and toward which the teeth carry thefibers when they enter the duct, the purpose of this edge being to causefibers discharged from the teeth to be diverted into the duct andprevent them from being carried around the cylinder under the usualstationary cover and back to the feed point by the air stream induced bythe rotation of the cylinder. In other Words, this edge serves as acutoff to prevent recycling of the fibers around the toothed cylinder.

However, I have found that fibers discharged from the cylinder teethwill occasionally drape themselves over the cutoff edge, each fiber thusdraped having one of its ends pulled toward the perforated drum by theair flow in the duct and having its other end pulled by the air streaminduced by the toothed cylinder rotation and which flows back under thecylinder cover toward the feed rolls. The center portion of such adraped fiber is in the region of the stagnation point in the split airflow, that is, on the surface of the cutoff edge formed by the duct. Theoccasional draped fiber assists in draping additional fibers due toadded friction, air turbulence, entanglement with the first fiber, etc.Very quickly, a build-up of fibers occurs on top of the first fiber onthe cutoff edge, until the accumulated clump of fibers is displaced fromthis edge in one direction or the other. That is, the accumulated clumpis deposited on the perforated surface of the rotating drum, eitherdirectly from the cutoff edge or by being cycled back to the feed pointof the toothed cylinder and then back to the duct. In either case, theresult is a mottled or splotchy web formed on the perforated drum.

In an attempt to avoid this difiiculty, highly polished edges have beenused at the cutoff and various radii of the cutoff edge have been tried,but these measures give no significant improvement.

The principal object of the present invention is to proice vide a.web-forming machine operable at high speed and which overcomes theabove-noted difiiculty.

According to the invention, I provide at the cutoff edge (that is, theaforementioned edge formed by the duct adjacent the periphery of thetoothed cylinder) a nozzle arranged to direct a flow of air counter tothe air stream induced by rotation of the toothed cylinder. Moreparticularly, I provide a source of air at superatmospheric pressure,and means forming at the cutoff edge a nozzle communicating with thissource for directing against the cylinder-induced air stream an air flowof sufiicient force to prevent the cylinder-induced air stream fromimpinging upon the cutoff edge. The air source associated with thenozzle may comprise means forming a plenum chamber from which the nozzleleads, and an air blower connected to the plenum chamber.

Thus, in the new web-forming machine, the nozzle introduces acounterflow of air which mushrooms against the air stream induced byrotation of the toothed cylinder and against the flow of fibers from thecylinder teeth, whereby the aforementioned stagnation point normallylocated at the cutofr edge is displaced to a point remote from thisedge. In this way, the fibers discharging into the duct from the toothedcylinder are prevented from contacting the cutoff edge.

For a better understanding of the invention, reference may be had to theaccompanying drawing in which the single illustration is a schematicview of a preferred form of the new web-forming machine.

Referring to the drawing, the reference numeral 10 designates a cylindermounted for rotation about its axis and carrying at its peripheralportion a series of closely spaced, external teeth 10a. The toothedcylinder 10 is mounted for rotation on a suitable frame (not shown) andhas a drive shaft 11 connected to a motor (not shown). Thus, the driveshaft 11 serves as a means for rotating the cylinder at high speed inthe direction indicated by the arrow, that is, counterclockwise asviewed in the drawing. The teeth 10a, as shown, have leading edges whichare not precisely radial but are inclined in the direction of rotationof the cylinder. The teeth 10a may be provided by a toothed Wire orwires wound around and secured to the cylindrical surface of thecylinder, as in a conventional garnett cylinder, it being understoodthat substantially the entire cylindrical surface of the cylinder 10 isclothed with teeth 10a.

The fibers for making the web are delivered to the peripheral portion ofcylinder 10 from one side thereof by a feeding device which, as shown,comprises a lap roll 12, a pair of feed rolls 13-14, and a stationaryinclined plate 15 on which the fibers pass from the lap roll to the nipbetween the feed rolls. The fibers F in mat form may be supplied to thelap roll 12 from a suitable lap (not shown), as will be readilyunderstood by those skilled in the art. The upper feed roll 13 isprovided with teeth, while the lower feed roll 14 has a substantiallysmooth cylindrical surface; and both of these rolls are rotatablymounted close to the periphery of toothed cylinder 10 and are positivelydriven in opposite directions, as indicated by the respective arrows.Thus, the feed rolls 13--14 continuously draw the mat of fibers F fromthe lap roll 12 and present these fibers to the teeth of the rapidlyrotating cylinder 10 where they are picked up by the teeth and carriedpartly around the cylinder axis, as will be described in greater detailpresently.

If desired, stripper and worker rolls 16 and 17, respectively, may bemounted adjacent the periphery of the toothed cylinder 10, asillustrated, and positively driven in the direction indicated by therespective arrows. However, these additional rolls 16-17 are not neededfor normal operation of the web-forming machine.

A stationary duct 19 is provided at the side of the toothed cylinderopposite the feeding device 1215. The peripheral portion of cylinder 10is disposed partly in the entrance end of duct 19 so that the duct isadapted to receive fibers discharged from the teeth 10a of the cylinder.The outer wall of the duct, opposite the periphery of cylinder 10, isprovided with perforations 20 for admission of air, as will be describedin further detail presently. The duct 19 extends generally tangentiallyfrom the peripheral portion of cylinder 10 in the direction of itsrotation and leads to the perforated cylindrical surface 21 of a drum,the perforations of the drum being shown at 21a. The drum 21 is mountedfor rotation about its axis on the machine frame and is provided with adrive shaft 22 connected to. a motor (not shown) and serving as a meansfor rotating the drum in the direction indicated by the correspondingarrow. At the end of the duct 19 adjacent the drum 21, sealing means areprovided between the duct and the drum periphery to prevent anysubstantial flow of air from the duct except through the perforations21a in the part of the drum periphery which is at the discharge end ofthe duct. Such sealing means may include a stationary seal 23 connectedto and extending along the edge of one wall of the duct close to theperiphery of drum 21, and a web roll 24 substantially filling the spacebetween the drum periphery and the near edge of the opposite wall of theduct, the roll 24 being rotatably mounted on the frame and having itsperiphery substantially in engagement with the drum periphery.

The. lower portion of the foraminous drum 21 is located in a closedchamber formed by a housing 25. The space between the top of housing 25and the periphery of drum 21 is closed at one side by the seal 23 and atthe opposite side by a flexible sealing flange 26 connected to thehousing and engaging the drum periphery. A suction fan 27 is connectedto the interior of the housing 25 and serves to evacuate air from theinterior of drum 21. Thus, a partial vacuum is maintained in the drum21, causing a flow of air through the holes 2% into the entrance endportion of the duct and thence through the duct and through theperforations 21a in that part of the cylindrical surface of the drumwhich is at the discharge end of the duct. This air flow induced by thesuction fan 27 acts to pick up the fibers discharged into the duct fromthe teeth of cylinder 10 and deposit these fibers in the form of a webon the perforated cylindrical surface of the rotating drum 21.

As the drum 21 rotates, the fibrous web W thus formed on the drumperiphery'is carried under the web roll 24 and is continuously removedfrom the drum surface by suitable means. As illustrated, the means forremoving the web from the drum surface comprises an endless belt orapron 28 mounted on rolls 29 and 30, one of these rolls being positivelydriven to move the apron in the direction indicated by the arrow. Afterpassing under the web roll 24, the web W passes from the drum 21 over aroll 31 and onto the upper part of apron 28, which carries the web awayfrom the machine. Within the drum 21 is a stationary baffle 32 ofarcuate form which is located close to the inner cylindrical surface ofthe drum, this bafile extending in an are approximately from the webroll 24 to the flexible seal 26. By means of the baffle 32, the suctioncreated by the fan 27 is inetfective at the region where the web W iswithdrawn from the rotating drum 21.

The upper portion of toothed cylinder 10 is enclosed partly by astationary cover 34- and partly by the duct 19, the outer wall of whichterminates at the cover 34. At its lower portion, the toothed cylinder10 is enclosed by a stationary cover 35, one edge portion of which isprovided with a flexible sealing flange 36 engaging the cylindricalsurface of the lower feed roll 14. The opposite edge portion of thelower cover is located adjacent an edge 19a formed by the duct 19 andwhich corresponds to. the cutoff edge previously described. The edge 19apartly defines the entrance end of the duct and extends lengthwise alongthe toothed cylinder 10a in closely spaced relation to the peripheralportion of this cylinder. As will be observed from the drawing, thedirection of rotation of cylinder 10 is such that its teeth 19a, uponentering the entrance end of the duct, move toward the duct edge 19a.The lower cover 35 serves as a means forming at the edge 19a a nozzle 37for directing a flow of air close to the cylinder teeth and counter tothe direction of rotation of the cylinder. By means of partitioning 38coactin-g with the lower cover 35 and the inner wall of duct 19, aplenum chamber 39 is formed from which the nozzle 37 leads. The plenumchamber 39 is adapted to contain air at superatmospheric pressuresupplied through a duct 40 from a blower 41.

It will be understood that the toothed cylinder 10 is substantiallyenclosed by means including the stationary parts 19, 34 and 35 and thefeed rolls 1314. The edge 19a and the adjacent nozzle 37, of course,extend lengthwise of the toothed cylinder along all of its toothedportion, as do the feed rolls 13-14. The various parts are dimensionedto handle any desired width of fiber stock delivered to the feedingdevice 12-15 and to discharge a web W of desired width.

The toothed cylinder 10 is driven at high speed to enable a highproduction rate, the foraminous drum 21 being driven at a relatively lowspeed which is such as to provide the desired thickness of the web W ofrandomly disposed fibers formed on the drum surface. As an example, thetoothed cylinder 1% may be driven so that its toothed peripheral portiontravels at a speed of about 7500 feet per minute.

In the operation of the machine as illustrated, the teeth 1G6: of therotating cylinder pick up the fibers F as they are fed to the cylinderand carry them partly around the cylinder axis. As the fibers enter theentrance end of duct 19, they are subjected to a combination of forcesincluding the centrifugal force tending to throw them radially outwardfrom the cylinder, the air flow toward the drum surface 21 at thedischarge end of the duct which is created by suction fan 27, and theair flow induced by the high speed rotation of the toothed cylinder andwhich is directed toward the duct edge 19a. As a result, the fibers aredischarged from the cylinder teeth 10a into the duct 19 at high speed,this discharge being generally tangentially of the cylinder and in thedirection of its rotation, that is, generally in the direction in whichthe duct 19 extends from the cylinder to the drum 21. Those dischargedfibers which are directed toward the duct edge 19a are met by theopposing air flow from nozzle 37 and deflected away from the edge 19aand into the duct 19 before they can contact this edge. Thus, the airflow from nozzle 37 prevents draping of a fiber over the edge 19a andthereby avoids the previously mentioned build-up of a clump of fibers onthis edge. The web W is continuously formed on the perforated drumsurface 21, as the drum rotates, and is continuously removed from thedrum by the discharge means 28-31, as previously described.

In the example given above, where the toothed cylinder 10 is driven at aperipheral speed of about 7500 feet per minute, measurements show thatthe velocity pressure in the air stream induced by the cylinder rotationat the duct edge 1921, when no air is blown through nozzle 37, isaproximately 3 /2" H O, which corresponds with the velocity pressureproduced by an air velocity of 7500 feet per minute. The total pressure(static plus velocity pressure) provided in the nozzle 37 by the blower41 should be in excess of the total pressure in the opposing air streamwhich would strike the edge 19a except for the air flow from the nozzle.In the above-noted example, nozzle plenum pressures of 5 to 7" H O givegood results.

As will be observed from the drawing, the perforations 20 in duct 19 aredistributed over the portion of the duct wall which is opposite thetoothed cylinder 10.

This arrangement has a distinct advantage in the new machine because itacts to reduce the over-all air turbulence adjacent the perforatedsurface or screen of drum 21, where the fibers from the toothed cylinderare deposited. In other words, this arrangement serves to avoid anuneven deposit of fibers on the drum screen 21, which would result in aweb W of irregular thickness.

I claim:

1. A web-forming machine comprising an externally toothed cylindermounted for rotation about the cylinder axis, a device for feedingfibers to the peripheral portion of the cylinder for engagement by thecylinder teeth, a rotating drum having a perforated cylindrical surface,a duct leading in a generally tangential direction from the peripheralportion of said cylinder to the perforated surface of the drum, saidduct forming an edge disposed in closely spaced relation to theperipheral portion of the cylinder at a region remote from said feedingdevice, suction means for maintaining a partial vacuum in the drum tocreate air flow in one direction through the duct and thereby drawfibers along the duct from the cylinder to said perforated surface toform a web thereon, means for rotating the cylinder at high speed in adirection to cause said teeth to pick up and carry fibers from thefeeding device partly around the cylinder axis into the duct and thentoward said edge, whereby said cylinder rotation induces in the duct anair stream tending to flow toward said edge and the fibres aredischarged in said generally tangential direction from the teeth intothe duct under the actions of centrifugal force, said induced air streamand the air flow created by the suction means, a source of air atsuperatmospheric pressure, and means forming at said edge a nozzlecommunicating with said source for directing an air flow counter to saidinduced air stream and counter to said direction of the air flow createdby the suction means, thereby preventing entrapment on said edge offibers discharged from the teeth.

2. A web-forming machine according to claim 1, in which said air sourcecomprises means forming a plenum 6 chamber from which said nozzle leadsand adapted to contain air at superatmospheric pressure.

3. A web-forming machine according to claim 1, in which said air sourcecomprises means forming a plenum chamber from which the nozzle leads,and an air blower connected to the plenum chamber.

4. A web-forming machine according to claim 1, comprising also means forcontinuously removing the web from said perforated surface of therotating drum.

5. A web-forming machine according to claim 1, in which said teeth areinclined in the direction of rotation of the cylinder.

6. A web-forming machine according to claim 1, in which said air sourceis operable to create in the nozzle a pressure substantially in excessof the opposing pressure of said induced air stream.

7. A web-forming machine according to claim 1, in which said feedingdevice includes a pair of coacting feed rolls adjacent the peripheralportion of the cylinder.

8. A web-forming machine according to claim 1, in which said feedingdevice includes a pair of coacting feed rolls adjacent the peripheralportion of the cylinder, and a lap roll for delivering fibers to the nipof said feed rolls.

9. A web-forming machine according to claim 1, in which the duct has afirst wall forming said edge and a wall located opposite said first walland partly defining a duct space into which fibers are dischargeddirectly from the cylinder teeth, said opposite wall having perforationsdistributed over that portion thereof which lies opposite the peripheryof the toothed cylinder.

References Cited in the file of this patent UNITED STATES PATENTS188,164 Miles et al Mar. 6, 1877 2,451,915 Buresh Oct. 19, 19482,676,363 Plummer et al Apr. 27, 1954 2,676,364 Plummer et a1 Apr. 27,1954 2,726,423 Harwood et a1 Dec. 13, 1955 2,876,500 Buresh et al Mar.10, 1959

